This glossary translates the CNC terms a beginner must understand before releasing a first project. Use it to distinguish machine coordinates from work zero, feed from spindle speed, runout from backlash, and a drawing from a controller-ready file.
Machine Parts and Motion Terms
The frame carries cutting loads; the gantry spans the work area; the Z assembly moves the spindle vertically; and the spoilboard is the replaceable surface beneath the stock. Leadscrews, belts, linear rails, bearings, and stepper motors belong to the motion system. These terms describe components, not guaranteed accuracy.
Coordinates, Homing, and Work Zero
Machine coordinates describe the controller's reference system. Work coordinates place the job origin on the stock. Homing establishes a repeatable machine reference when the hardware and controller support it; setting work zero tells the program where the design begins. The two operations are related but not interchangeable.
CAD, CAM, Post-Processors, and Senders
CAD creates geometry. CAM turns geometry into toolpaths with a defined tool, depth, direction, and strategy. A post-processor formats those toolpaths for a controller, while a sender transfers or streams the resulting instructions. An attractive drawing is therefore not yet a machine-ready file.
Cutters, Collets, Flutes, and Stick-Out
The collet grips the cutter shank, not the cutting edge. Flutes form cutting edges and chip space. Cutting diameter controls feature access and inside radius, while excessive stick-out reduces stiffness. Shank size, flute length, cutting length, and collet compatibility should be recorded separately.
Feeds, Speeds, Chip Load, and Stepdown
Feed rate is linear motion through the material; spindle speed is rotational speed; chip load estimates material removed by each cutting edge; depth of cut is axial engagement; and stepdown is the layer depth chosen in CAM. None of these values can be transferred safely without matching the tool, material, machine, and engagement.
Workholding, Runout, Tramming, and Finish
Workholding keeps stock from translating, lifting, or rotating under load. Runout describes off-center tool rotation. Tramming aligns the spindle axis with the work surface. Backlash, deflection, tearout, chatter, burrs, and burning describe different failure mechanisms and should not be treated as synonyms for a poor finish.
This step sits within From CAD to CAM to the CNC Sender: How the File Actually Moves; continue with What CNC Beginners Should Read—and Leave Alone—in G-Code and How Much CNC Work Area Do You Need? A Stock-to-Setup Calculator when the project reaches the neighboring decision.
40 Core CNC Terms in Plain English
| Term | Plain-English definition | Why it matters | Related guide |
|---|---|---|---|
| Axis | A controlled direction of machine motion. | Identifies where movement or error occurs. | Keep CNC Machine Limits and Software Limits From Ruining the Job |
| Backlash | Lost motion when a drive reverses direction. | Can shift dimensions and repeated positions. | Why Your CNC Cuts the Wrong Size—and What to Measure First |
| Ball screw | A screw-and-ball drive that converts rotation into linear travel. | Drive design affects load, motion, and maintenance. | How CNC Rigidity and Motion Systems Affect Cut Quality |
| CAD | Software or data used to create geometry. | A drawing is the editable design source, not machine motion. | From CAD to CAM to the CNC Sender: How the File Actually Moves |
| CAM | Software that turns geometry and process choices into toolpaths. | It assigns tools, depths, entries, and operations. | From CAD to CAM to the CNC Sender: How the File Actually Moves |
| Chip load | Estimated material removed by one cutting edge per revolution. | It connects feed, RPM, and flute count. | Build a CNC Feeds-and-Speeds Experiment Log You Can Reuse |
| Climb cut | A cut where tool rotation pulls into the advancing material. | It changes force direction and edge behavior. | How Wood Species Change CNC Cutting and Finishing Decisions |
| Collet | The precision sleeve that grips a matching tool shank. | Dirt, wear, or mismatch can create runout. | Measure CNC Spindle Runout Before Replacing the Collet |
| Conventional cut | A cut where tool rotation opposes the advancing material. | It loads the edge differently from climb cutting. | How Wood Species Change CNC Cutting and Finishing Decisions |
| Cutter diameter | The nominal width of the cutting portion of a tool. | It limits internal radii, detail, strength, and chip space. | How Bit Diameter and Flute Count Trade Detail for Strength |
| Datum | A physical or geometric reference used to locate features. | Repeat setups depend on preserving the same reference. | A CNC File Handoff Checklist for Units, Origin, Geometry, and Post-Processors |
| Deflection | Elastic movement of a tool, stock, fixture, or machine under force. | It changes dimensions and finish while load is present. | How CNC Rigidity and Motion Systems Affect Cut Quality |
| Depth of cut | The axial depth engaged in a cutting operation. | It contributes to tool load and chip evacuation demand. | Plan CNC Depth of Cut and Stepdown Without Overloading the Tool |
| Feed rate | Commanded linear travel per unit time. | Together with RPM and flutes, it shapes effective chip load. | Build a CNC Feeds-and-Speeds Experiment Log You Can Reuse |
| Fixture | A device that locates and holds stock repeatably. | It controls force, datum, access, and batch consistency. | Which CNC Workholding Method Fits the Part—Clamps, Tape, Fixtures, or Vacuum? |
| Flute | A cutting edge and its associated chip space on a tool. | Flute count affects chip space and feed planning. | How Bit Diameter and Flute Count Trade Detail for Strength |
| G-code | Controller instructions for motion and machine functions. | It can create real motion and must match the controller. | What CNC Beginners Should Read—and Leave Alone—in G-Code |
| Gantry | The structure spanning the work area and carrying motion components. | Its stiffness and alignment affect usable cutting behavior. | How CNC Rigidity and Motion Systems Affect Cut Quality |
| Homing | A supported routine that establishes a repeatable machine reference. | It is not the same as setting the job origin on stock. | Before Your First CNC Project, Check the File, Zero, Clamps, and Dry Run |
| Jog | A manual or software command for controlled axis movement. | It is used for setup but can still cause collisions. | Before Your First CNC Project, Check the File, Zero, Clamps, and Dry Run |
| Kerf | The material width removed by a cutting process. | It affects fit and the dimensions of profiles or openings. | Why Your CNC Cuts the Wrong Size—and What to Measure First |
| Machine coordinates | The controller's position relative to its machine reference. | They define travel independently from the current job zero. | Keep CNC Machine Limits and Software Limits From Ruining the Job |
| Origin | The reference point from which file or job coordinates are interpreted. | A wrong origin can place correct geometry in the wrong location. | A CNC File Handoff Checklist for Units, Origin, Geometry, and Post-Processors |
| Plunge rate | The commanded feed for entry along the tool axis. | Axial entry can load a cutter differently from lateral cutting. | Plan CNC Depth of Cut and Stepdown Without Overloading the Tool |
| A recessed area cleared inside a closed boundary. | It requires suitable entry, stepdown, clearing, and finish strategy. | Choose CNC Router Bits by the Job, Not the Catalog | |
| Post-processor | A translator that writes CAM output for a specific controller. | A wrong post can change commands, units, or unsupported behavior. | A CNC File Handoff Checklist for Units, Origin, Geometry, and Post-Processors |
| Probe | A sensing device or routine used to locate a surface or feature. | It can establish references only when its method and offsets are verified. | How to Square, Tram, and Surface a CNC Router |
| Profile | A toolpath that follows the outside or inside of a boundary. | Side choice, allowance, tabs, and cut order control the released edge. | Choose CNC Router Bits by the Job, Not the Catalog |
| Rapid move | Non-cutting motion commanded for positioning. | Rapids must clear stock, clamps, fixtures, and machine limits. | Before Your First CNC Project, Check the File, Zero, Clamps, and Dry Run |
| Runout | Off-center rotation measured at a tool or spindle interface. | It changes effective diameter, finish, load, and fine-feature accuracy. | Measure CNC Spindle Runout Before Replacing the Collet |
| Sender | Software or hardware that delivers machine instructions to a controller. | Transfer, feedback, and disconnect behavior affect job control. | Should You Run a CNC From an Offline Controller or a Computer? |
| Shank | The portion of a cutter held by the collet or holder. | Its size and condition must match the toolholding system. | Choose CNC Router Bits by the Job, Not the Catalog |
| Spindle speed | Rotational speed of the cutter, commonly stated in RPM. | It works with feed, flutes, engagement, and material response. | Why CNC Spindle Wattage Does Not Predict Real Cutting Capacity |
| Spoilboard | A replaceable working surface beneath the stock. | It provides support and a surface that can be machined or sacrificed. | Build and Surface a CNC Spoilboard That Stays Useful |
| Stepdown | The axial layer increment selected between toolpath levels. | It determines how total depth is divided into passes. | Plan CNC Depth of Cut and Stepdown Without Overloading the Tool |
| Stepover | The lateral spacing between adjacent toolpath passes. | It changes scallop height, load, clearing time, and finish. | Choose CNC Router Bits by the Job, Not the Catalog |
| Stock | The raw material before the programmed operation. | Its real size, condition, and identity belong in the setup. | How to Choose a CNC Router Around Your Real Projects |
| Toolpath | The programmed path and operation followed by the cutter. | Direction, depth, entry, order, and clearance create different outcomes. | From CAD to CAM to the CNC Sender: How the File Actually Moves |
| Tramming | Aligning the spindle axis with the working plane. | Poor tram can create ridges, tapered walls, and depth variation. | How to Square, Tram, and Surface a CNC Router |
| Work zero | The job coordinate reference set on the stock or fixture. | Every programmed position is interpreted from this job reference. | Before Your First CNC Project, Check the File, Zero, Clamps, and Dry Run |
Questions About CNC Router Terms Beginners Need Before Their First Setup
What is the difference between machine zero and work zero?
Machine zero belongs to the controller's machine-coordinate reference. Work zero places the program origin on the stock. Homing may establish machine zero; the operator still sets or restores the work coordinate used by the job.
Is CAM the same as a CNC sender?
No. CAM creates toolpaths and posts machine instructions. A sender communicates those instructions to a supported controller. Some applications combine functions, but the roles remain different.
What does cutter stick-out mean?
Stick-out is the distance the cutter projects from the collet. Extra projection may reach a feature but reduces stiffness and can increase deflection or chatter.
